A kidnapped boy. Impenetrable circumstances. A case for Sherlock Holmes. The son of Count Schönburg disappears from the garden of the family villa in broad daylight. It quickly becomes clear that he is the victim of a kidnapping and that his life is hanging by a thread. Sherlock Holmes and Dr. Watson travel to Vienna to take on the case. Their investigations initially focus on the immediate environment. The relatives, with whom the Schönburgs have had no contact for years, have a number of skeletons in their cupboards and do not seem particularly upset about the boy's misfortune. The master detective's enquiry uncovers a host of suspects with strong motives, but no concrete evidence - and every day without a solution puts the boy in increasing danger.